The Mitsubishi A6M Zero
By Chuck Hawks
It is hard for modern researchers to understand just how dominant the A6M Zero fighter was in the early years of the Pacific War. No Allied plane could stand against it. The obsolete Brewster Buffalo and the sleek looking, but comparatively low performance, Bell P-39 fared poorly against the Zero. The best of the early American Army fighters was probably the Curtiss P-40 and the early models of this fighter were distinctly inferior in most respects to the Zero. Even the contemporary models of the famous British Supermarine Spitfire and Hawker Hurricane fighters, which had won the Battle of Britain, had major problems with the Zero when they met in 1942.
At sea, the situation was hardly much better. The U.S. Navy's Grumman F4F Wildcat carrier fighter was out classed by the Zero, although it probably provided the best competition of any of the Allied fighters in the theater. Navy and Marine pilots used the stubby fighter's maneuverability and ruggedness to good advantage in the desperate early battles in the Pacific.
Most of the top Japanese Navy aces flew the Zero. Prominent among them is Saburo Sakai (with 64 victories), the top scoring Japanese ace to survive the war, and Hiroyoshi Nishizawa (actual total of victories unknown, but probably around 104), perhaps the greatest Japanese ace of them all. Among other Japanese aces, Shoichi Sugita had 120+ claimed victories, Tadashi Nakajima 75+, Naoishi Kanno 53, Teimei Akamatsu 50+ and Kinsuke Muto 35.
Not only could the Zero out-dogfight any Allied fighter, it also out-ranged them. Many people do not realize that the Zero was the world's first long range escort fighter. Zeros flew long range bomber escort missions during the war in China, before the Pacific war even began, and throughout WW II Japanese carrier air groups out-ranged their US counterparts, primarily because of the great range of the Zero fighter.
If the Germans had the long range Zero during the Battle of Britain, instead of the short range ME 109, the outcome might have been very different. As famous as the Zero was, it is probably still under-rated by most people.
The Zero was designed by Jiro Horikoshi to fulfill Japanese Navy requirements for great range, rapid climb, high speed and above all superior maneuverability. These were the characteristics desired by Japanese fighter pilots. (My father, an AAF aeronautical engineer during WW II who was involved in the development of the P-38, P-40 and later P-51 series fighters, was honored to meet Mr. Horikoshi after the war.)
In order to achieve its performance goals the Zero was designed with a very low wing loading. Weighty items, such as armored glass, pilot armor and self-sealing fuel tanks, were eschewed. Even the Zero's aluminum skin was thinner than normal. Often, the fighters' radios were removed in the field to further lighten the aircraft.
Japanese fighter pilots generally chose not to wear parachutes in combat, even when ordered to do so. Such men gladly sacrificed defensive features in order to achieve a fighter with superior agility. (Safety features were progressively added in later Zero models and by 1944 the A6M5 series Zeroes were better all-around fighters, but by then they were outclassed in most respects by newer Allied fighters.)
For those of you who are unfamiliar with this wing loading thing, let me make a comparison between a couple of birds with which almost everyone is familiar. Doves fly fast and are very acrobatic birds. They have a low wing loading. Ducks fly fast and can dive like a stone, but they are not very acrobatic. Ducks have a high wing loading. The former have a lot of wing lift for their body weight; the latter have a lot of body weight compared to their wing lift.
The Zero's performance fell off at high altitudes, but the American fighters that opposed it early in the war were even worse in that regard. At low and medium altitudes, nothing could touch the Zero.
The first production version of the Zero was the A6M2 (officially the Type 0 carrier fighter Model 11) of 1940. This had a Nakajima Sakae 12 engine, a 14-cylinder air cooled radial that developed 950 hp. at 13,800 ft. The similar Model 21 had folding wing tips for aircraft carrier use. This was the model on board the Japanese carriers at the beginning of the Pacific War on December 7, 1941. It was also the model captured almost undamaged in the Aleutians in 1942 and examined in detail by American engineers. (See photo at the top of this page.)
The A6M2 (Model 21) had a top speed of 331 m.p.h. at 14,930 ft., initial climb rate of 3,100 ft./min. and a range of 1,265 miles on internal fuel. With an under fuselage drop tank the range was extended to 1,930 miles. The standard Zero armament was two 7.7mm machine guns in the engine cowling and a 20mm, short barreled, drum fed cannon in each wing. Wingspan was 39 ft. 4.5 in. The empty weight was 3,704 pounds and loaded weight was 5,313 pounds.
The next main version of the Zero was the A6M3 (Type 0 Model 32), which appeared late in 1942. This version was powered by an up-rated 1,130 hp. Sakae 21 radial engine with a two stage supercharger that improved high altitude performance. Top speed was increased to 336 m.p.h. at 19,865 ft., which was slower than the latest Allied fighters. Best climb rate was 4,500 ft./min. Armament remained the same, although a long barreled cannon was introduced in the Model 22-ko.
By this time, the American AAF had high altitude P-38F/G Lightnings to augment the improved P-40E/F models facing the Japanese fighters. The Allied fighters used their superior speed, roll and dive rates to "hit and run," a tactic that negated the Zero's superior climb and turning ability. The rule for Allied pilots was "never turn with a Zero." Instead, they would attack from above, shoot and dive away. The speed gained from the dive could be used to exit the area, or converted into altitude in a gentle climbing turn that ultimately put the Allied fighter above the Zero for another firing pass.
The A6M3 Model 32 had clipped wing tips, achieved by basically removing the folding wing tips of the Model 21. This was intended to improve the roll rate, which was inferior to that of American fighters. This model also had reduced internal fuel capacity (down to 134 gallons from the 156 gallon capacity of the A6M3 Model 22 with rounded wing tips). The Zero was beginning to show its age.
The A6M5 (Type 0 carrier fighter Model 52) of 1943-1944 probably represents the design peak of the Zero fighter. In response to the continually improving performance of the latest Allied fighters, this model had an improved Sakai 31 engine with ejector exhaust stacks to augment thrust, a new wing without folding tips and the reduced wing span of the Model 32, but with the familiar rounded tip shape of earlier Zeros, plus heavier skin to improve dive speed and durability.
The A6M5-ko featured belt fed 20mm cannons with a greater ammunition supply. The contemporary A6M5-otsu featured armor-glass, CO2 fire-extinguishers for the fuel tanks and a 13.2mm machine gun in the cowl replaced one of the 7.7mm machine guns.
The A6M5-hei added pilot armor and a self-sealing fuel tank behind the pilot. Armament was again increased, this time to a single 13.2mm machine gun in the cowl plus two 13.2mm machine guns and two 20mm cannons mounted in the wings.
The accumulated increased weight of the A6M5 series increased the wing loading, which negatively impacted maneuverability. Specifications for the A6M5-ko included a top speed of 351 m.p.h. at 19,685 feet. Best climb rate was 3,340 ft./min. The empty weight was 4,136 pounds and the normal loaded weight 6,025 pounds.
The specifications that follow are for the A6M5 Model 52 of late 1943.
The dive limiting speed was raised to 460 m.p.h. By this time the performance of the Zero had, in most respects, fallen well below that of its contemporary major adversaries, the P-38J Lightning, F6F Hellcat and the F4U Corsair. It remained, however, a very dangerous opponent in a "turn and burn" dogfight.
The final production version of the Zero was the A6M7 (Type 0 Model 63) of 1945. Features included a Sakae 31-ko radial engine with water-methanol injection, self-sealing wing tanks and the five gun armament of the A6M5-hei. Increased structural strength allowed a 551 pound bomb to be carried in the fighter-bomber role, but it was too little too late.
The Zero had fallen behind and more advanced Japanese Navy fighters were in service by 1944. These included the land based Mitsubishi Raiden series interceptors (also designed by Jiro Horikoshi) and the Kawanishi N1K2-J Shiden-KAI high altitude fighter.
The Zero was a landmark fighter when it was introduced, perhaps the best in the world. However, like the Hawker Hurricane and the Curtiss P-40, it lacked the development potential of some of its contemporaries, such as the British Spitfire and German ME 109.
In addition, the Japanese were slow to implement needed improvements. The A6M5-hei of 1944, for example, incorporated improvements that most U.S. fighters had received in 1942. The Zero's period of superiority could have been extended had the Japanese been able to implement improvements more rapidly.
Japan also lacked the industrial potential to produce aircraft of all types, particularly fighters, in sufficient quantity. A total of 10,936 Zero fighters of all types were produced.
That is a lot of airplanes, but it pales in comparison with the (approximately) 13,700 P-40's, 12,200 Hellcats, 12,500 Corsairs, 15,300 P-47's, 10,000 P-38's and 15,000 P-51's produced in the US for the Navy, Marines and AAF that constituted its main opponents. (Not to mention British Hurricanes and Seafires.) The majority of the land based Allied fighters were sent to the European Theater, but it is worth noting that Japanese fighter pilots were forced to fight from a position of numerical inferiority for most of the war.
Even given its technical and numerical inferiority, in the hands of an accomplished pilot the Zero remained a formidable adversary right to the end of the war. For example, the Japanese ace Saburo Sakai blundered alone into a formation of 15 Hellcats during the defense of Iwo Jima. By that time Sakai was debilitated by war wounds and blind in one eye, but in a long running dogfight the Hellcat pilots could not nail his agile Zero fighter. In fact, after he finally made it home, completely exhausted, his astonished ground crew inspected his plane and discovered that not a single enemy bullet had hit the ace's Zero!
In his book Samurai Saburo Sakai tells the story of another incredible air battle. In February 1945 the ace Kinsuke Muto, alone in his Zero, attacked 12 Corsair fighters. In the course of the wild dogfight that ensued, Muto shot down four Corsairs before running out of ammunition and escaping. Such battles, like the Zero fighter itself, are the stuff of legend.
Copyright 2003, 2017 by Chuck Hawks. All rights reserved.